Question

2. Please determinate the correctness of the following statements and justify your answers (preferably by examples). (5 Points)

a. HTTP services have to be offered at port 80

b. DNS services are usually offered at port 53 through UDP.

c. An attacker has to use existing transport-layer protocols to make sure the packets are routed through the Internet. d. If an attacker uses UDP as the transport-layer protocol, he cannot implement reliable, connection-oriented networking service.

Answer 1

1. No this is not mandatory that HTTP services can only be given at port 80 because we can provide the services at other port as well but the user will need to remember the port number on which we are working. Thus in order not to remember the port number we are making a general port number.

2. Yes, it is correct that DNS is generally implemented at port 53.

3. Yes, it is true that attacker has to use the same protocol in order to attack because he has to route the packets through the internet where the user is present so in order to communicate with the user the packets are to be present in the same internet.

4. No, If the user UDP, then one can have a reliable connection by implementing algorithms on the application layer. Thus we can have reliable connection-oriented connection.

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